FILE PHOTO: A general view of the Fortum headquarters in Espoo, Finland August 18, 2017. REUTERS/Lefteris Karagiannopoulos/File Photo

Fortum in September clinched a deal to buy E.ON’s (EONGn.DE) 46.65 percent stake in Uniper, but then launched a full offer to all shareholders due to German takeover rules. Uniper has considered the bid as hostile and too low.

The number of shares tendered on top of E.ON’s stake will determine whether Fortum can get a controlling stake in Uniper.

E.ON can sell its stake by Jan. 11 while all other shareholders can tender shares by Jan. 16.